Photocell



Oct. 8, 1940. I o, GEISLER 2,217,402

PHOTOS-ELL Filed Sept. 19,- 1935 TRANSPARENT METAL COATING THl/V COAT/M 0F METAL OF IRON GROUP- 8455 puns 0F mm MET/1L 1e. ALUMINUM mVENTbR.

OTTMAI? GEIYSLER BY I 1 I I I f I ORNEY.

Patented Oct, 8, 1940 UNITED: STAT:

PHOTOCELL Ottmar Geisler, Nuremberg, Germany, assignmto Siiddeutsche Apparate-Fabri k, G. m. b. IL,

. Nuremberg, Germany Application September 19,1935, Serial No. 41,201 In Germany October 17, 1934 v Some photocells with a selenium insulating coating are known to the art in which a selenium coating is welded onto a base plate made of some metal of the'iron group, which coating is trans-.1

" 5 formed fromthe amorphous condition into the grey crystalline condition through different heat v processes, and the free surface of which isthen covered with a transparent metallic film.

If ra'ys strike the selenium coating through the transparent metallic film, an electromotive force is produced thereby which is proportionate; to the rays striking the cell.

The known selenium photo elements are frequently built into a housing together with a seinl5 sitive movable coil instrument, serving in. this way as a brightness meter. In anfassembly of this kind the magnetic circuit of the movable coil instrument can be easily influenced due to .the

presence of the photocell with an iron base plate. By means of the photocell according to the present invention this disadvantage, which has to be contended with in the assembly 'ofthe known cell with a movablecoil instrument, is overcome. a a 4 The reason is that in this photocell. the base plate to which iswelded the. semi-conductive coating, especially the selenium coating, is made of a light metal, which is covered witha thin coating of metal of the iron group as shown by the single figure illustrating an embodiment'of my invention. A nickel-plated aluminum plate is especially suitable as the base metal of the photocell" according to the present invention.

' In order to obtain a most perfect contact bethe base plate and the selenium coating tween to be welded onto the former, the aluminum plate is appropriately roughened mechanically or f chemically before it is nickel-plated.

It is necessary to cover the aluminum plate alow contact resistance between the base plate' and the selenium coating. If'the selenium coat ing were tobe-welded directly onto the aluminum baseplate. then the 'face of said base plate, a crystallized semi-conductive. layer of light sensitive selenium mechah which is a thin coating with a metal of the iron group in order to obtain,

'4 Claims. (01,}36-89) aluminum plate would forma highresistance be; tween the base plate and the selenium coating.-

Consequently the nickel-plating-of the a1umi-' numbase plate must be so carried out according to one .of the known methods that. it will' not be 5 .POSSlbIC for any oxide coating to. form between- 'th'ealuminum plate-and the nickel coating;

With such a cell with a'.,base plate madeof light metal the magnetic system offa movable coil instrument can not be influenced.- More-l0 over, this cell, as compared to the known cell,- has the additional advantage of beinglighter.

' The cell according to the present. invention is) also-superior to the known cells having an iron base plate in vother cases, for instance in. an 15 asse my of a photocellwith a magnetic needle.

whatI'claimisz H L-A photocell. comprising 'a rigid base plate of light non-ferrous metal on one surface of which is-a thin coating of nickeLa-crystallized m selenium layer mechanically weldled'to said we ing, and a 'thin, light-permeable film of relatively' chemically inactive metal in intimate contat withthe oppositesurface ofsaid-seleniuin'layer. 2. A photocell according to claim -1, wherein base plate which is covered the surface of the with s'aid'thin layer 'of nickel is of rough form.

L3. Aph'otocell comprising a rigid'base'plate'of aluminum, a thin coating of nickel on one surically welded to said coating, and a thin, lightpermeable iilmof relatively chemically inactive; metal in intimate contact with the opposite sur face of said selenium layer. 4

: '4.-A photocell comprising a rigid base plate of light non-ferrous metal on'one surface of ofa;v metal of 'the'irongroup, a crystallized selenium layer'mechanically welded to said "coating, and a thin, light -per- 40 meable film of relatively chemically. inactivemetal in intimate contactwithfthe opposite, sur-' face'of said selenium layer.

omsnna. 

